Is one of the music instrument serie developed by the Abylight company for the DSiware, it costs 500 Nintendo points, so it's not a free app. But the good thing about this "game" is that you actually can use it for Jam Sessions as well, because it has some Chords transpose who can be controlled by the DSi pad. It also include a set of preset drums/riddims, such as Reggae, Ballad, SimfRock, Polk Ska and Samba... pretty basic.
Another nice feature is that you can Save/Load your "songs", so you record a melody and then can save the melody aswell and you can play over the melody you recorded.
While your playing, you can HOLD L/R and move the stylus around and do a note slide up/down depend on what movement you do with the stylus around the screen.
You can control the tempo, mute instruments/drum while your playing a Reggae, Ballad or whatever and Riddim. The keyboard it shows 2 Octaves, but you actually have 6 Octaves.
It have 16 instruments such as Banjo, Pino, Organ, Violin, SynthBrass, etc... and you can set 5 instrument at time. That mean you can use/change to another instrument with just clicking the number you set the instrument. This option is usefull for Jam and while your recording.
It's a good/nice app to mess around, but you have to considerate that it cost money... well...nintendo points.